Anyone play Soldat?
A very addictive online multiplayer side-scrolling shooter. Has excellent physics and tons of game types, servers, mods, and a single-player mode that let's you go against bots. But, the online experience is where it's at. Your character can jump, roll, crouch, go prone, and use jet packs attached to your feet. Do a jetpack roll, go prone in the air then use your jets, whatever you like.
Did I mention it's free?
You can register for fifteen bucks to get some extra features, such as forum access, and jet flame colors.
http://www.soldat.pl/en/
My name on there is Baggins.